The present invention relates to a bipolar integrated circuit and, more particularly, to an output driver circuit used as an interface driver and the like.
In general, a single NPN transistor is employed as an output driver circuit used as an interface driver and the like. However, the use of a single NPN transistor entails the risk that if the collector and a power source are short-circuited, a large current exceeding the maximum value in the safe operating range begins to flow between the collector and emitter resulting in transistor break down. In such an abnormal condition, there is also the danger that the transistor will generate increased heat and that its temperature will exceed the safe junction temperature, again resulting in the transistor breaking down.
Accordingly, an output driver circuit using a single NPN transistor possesses the drawback wherein it is easily rendered inoperative by an excessive output current or by excessive temperature.